Abstract: As an essential part of the performance improvement of lithium metal batteries, the acquisition of dense (LiF-rich solid electrolyte interphase (SEI)) has always been an urgent problem to be solved. Herein, we synthesized Zeolitic Imidazolate Frameworks (ZIFs) modified by two different functional groups (-NH₂, -CH₃) and used them as the fillers of polyethylene oxide (PEO) composite solid electrolytes to explore the catalytic effect of groups on LiF generation at the Li/electrolytes interface. In a LiFePO₄||SPE||Li cell test, the PEO-ZIF-NH₂ with LiF-rich SEI exhibits enhanced cycling performance, which was 3.8 times longer than that of PEO-ZIF-CH₃. The formation mechanism of LiF-rich SEI was investigated using first-principles calculation, revealing that ZIFs-NH₂ makes the C-F bond in TFSI^- longer compared with ZIFs-CH₃, which leads to easier breakage of the C-F bond and promoted the formation of LiF. The simple design idea of using organic catalysis to generate more stable SEI provides a new aspect for preparing high-performance lithium metal batteries.

Key words: LiF-rich SEI, Organic catalysis, Functional groups, Hydrogen bond, Difunctional MOF